# Where to download free 3D models to print (and the licenses to respect) > The most popular sites for downloading free 3D models to print, and how to read each model's license before you use it, modify it or sell the prints. Creative Commons licenses explained in brief. Source: https://simplebuild.it/tutorial/modelli-3d-gratuiti Author: SimpleBuild, Build simple. Deliver value. Category: 3D printing Procedure verified on: 2026-09-29 Free 3D models are found mainly on **Printables**, **Thingiverse** and **MakerWorld**; for anatomy and science there is **NIH 3D**, for artworks and museum objects the **Smithsonian**. But free doesn't mean "no rules": every model has a **license** that says whether you can modify it, republish it or sell the prints. Always read it before using the model. ## Before you start - **File format**: to print you need files such as **STL**, **3MF** or **OBJ**, which you open in the **slicer**, the program that turns the model into instructions for the printer (the G-code). The Prusa Knowledge Base names exactly these three formats. - **Ready-made G-codes**: some sites also offer files that are already "sliced". Use them only if they were made for your printer and your material. - **Create an account** on the site, if it asks for one to download. - **Look at photos of real prints** and the comments: they tell you whether the model prints well. ## The main sites ### Printables This is Prusa Research's model site. Anyone uploading a model must choose a free license (Creative Commons, GNU or BSD) and, according to the terms of service, anyone downloading must use the model in line with the license the author chose. The Prusa Knowledge Base points out that many models are under Creative Commons licenses with restrictions, such as the requirement to credit the author or a ban on commercial use. ### Thingiverse It is one of the oldest and largest sites. The Prusa Knowledge Base lists it among the alternatives, along with other sites that have both free and paid models. Here too each author chooses the license for their model: look for it on the page and read it before downloading. ### MakerWorld This is Bambu Lab's model site. The guidelines for uploaders ask them to choose the right license and forbid, for example, publishing modifications of models with a "No Derivatives" license or changing the license of a "ShareAlike" model. On MakerWorld you'll also find licenses other than Creative Commons, with their own rules: always read what is written on the model's page. ### NIH 3D This is the platform of the US National Institutes of Health (NIH) with scientific models: cells, viruses, proteins, anatomical structures, prosthetics, lab equipment. Its terms explain that many models are in the public domain or under Creative Commons licenses such as CC BY, but others have stricter rules: **each model has its own license**. Also, NIH 3D doesn't enforce licenses on the authors' behalf, so checking is up to you. ### Smithsonian 3D The Smithsonian, the US museum institution, has released millions of 2D and 3D images from its collections as **Open Access** under a **CC0** license, meaning with no copyright restrictions. The 3D models are on the 3d.si.edu website. Before printing one, open it in the slicer and check that it doesn't report errors. ## Creative Commons licenses, in brief Creative Commons licenses are made of "building blocks". Here is what each one means, according to creativecommons.org: - **BY (Attribution)**: you must credit the author. - **SA (ShareAlike)**: if you publish a modification, it must have the same license as the original. - **NC (NonCommercial)**: no commercial use. - **ND (NoDerivatives)**: no published modifications. The six combinations: - **CC BY**: the most open. You can do almost anything, including commercial use, as long as you credit the author. - **CC BY-SA**: like CC BY, but modified versions must have the same license. - **CC BY-NC**: you can modify and share, but not for commercial purposes. - **CC BY-NC-SA**: noncommercial, and modifications under the same license. - **CC BY-ND**: commercial use too, but without modifications. - **CC BY-NC-ND**: the most restrictive. You can only share it as it is, for noncommercial purposes. Then there is **CC0**: the author waives all possible rights and you can use the model for any purpose, without asking permission. ### How to credit the author When the license requires attribution (BY), write wherever you publish the print or the modified model: the model's name, the author's name, a link to the original page and the license name. For example: "Pen holder by Mario Rossi, from Printables, CC BY 4.0 license". ## What you can do, case by case - **Print for yourself**: fine with almost all licenses. - **Give a print to a friend as a gift**: that is noncommercial use; but if you do it to promote a business and the license is NC, ask the author first. - **Sell the prints**: only with licenses that allow commercial use (CC BY, CC BY-SA, CC BY-ND, CC0), respecting the other conditions. With NC, ask the author. - **Modify and republish**: not with ND; with SA keep the same license; with BY credit the original author. - **Re-upload the original file to another site**: avoid it, even when it's allowed. Better to link to the original page. If the downloaded model shows errors in the slicer, see [how to repair an STL file that won't print](https://simplebuild.it/tutorial/riparare-file-stl). To choose the right material, read [PLA, PETG or ABS: which filament to choose](https://simplebuild.it/tutorial/filamento-pla-petg-abs). ## If it still doesn't work - **You can't find the license**: look for it at the bottom of the model's page or in the files tab. If it isn't there, treat the model as "all rights reserved" and ask the author. - **The model doesn't print well**: read the comments and photos from people who have already printed it; you often find the right settings. - **The file is in a format the slicer won't open**: look on the same page for an STL or 3MF version. - **You need a part that doesn't exist**: no site has everything. If you need a custom spare part or a model to sell without license issues, a technician can design it from scratch for you. ## Frequently asked questions ### Can I sell prints of a model I downloaded for free? Only if the license allows it. With NC (noncommercial), no; with CC BY or CC0, generally yes, crediting the author when the license requires it. If in doubt, ask the author. ### If I modify a model, does it become mine? No. The modification is a derivative work: with ND you can't publish it, with SA you must use the same license as the original, and with BY you must credit the author. ### Which file should I download for my printer? Usually STL or 3MF, which you open in the slicer, the program that prepares the print. A ready-made G-code is fine only if it was made for your exact printer. ### Are NIH 3D anatomical models suitable for medical use? No. NIH 3D states that the models are for illustrative and educational purposes, not for diagnosis or treatment. ## Sources - [Where can you get 3D models, Prusa Knowledge Base](https://help.prusa3d.com/article/where-can-you-get-3d-models_2179) - [Terms of Service of Printables.com, Prusa Research](https://www.prusa3d.com/page/terms-of-service-of-printables-com_231249/) - [MakerWorld Model Upload Guidelines, Bambu Lab Wiki](https://wiki.bambulab.com/en/makerworld/tutorials/model-upload-guidelines) - [Thingiverse](https://www.thingiverse.com/) - [About NIH 3D](https://3d.nih.gov/about) - [NIH 3D Terms and Conditions](https://3d.nih.gov/terms) - [Smithsonian Open Access, Registry of Open Data on AWS](https://registry.opendata.aws/smithsonian-open-access/) - [About CC Licenses, Creative Commons](https://creativecommons.org/cc-licenses/) - [CC0, Creative Commons](https://creativecommons.org/public-domain/cc0/)